Remote keyless entry systems for vehicles are used to provide operators the ability to remotely lock and unlock doors, to provide an extended communication range to start a vehicle engine, among other functions. To accommodate the remote keyless entry system, an antenna to receive remote keyless entry signals is located in a vehicle. Because vehicle manufacturers are concerned about parts count, size, and cost of components in production vehicles, the vehicle manufacturers desire to consolidate components wherever possible to reduce costs and weight, and to save space in the vehicle.
Consolidating antennas in vehicles has routinely been performed for receiving radio frequency bands, including AM and FM bands. There are many types of antennas, where different antenna types are used for different frequency bands. Whip antennas, which are typically stiff but flexible wire antennas, are usually vertically mounted, monopole antennas and configured to receive for AM/FM band signals.
Remote keyless entry (RKE) systems generally use antenna types other than whip antennas since the frequencies over which the remote keyless entry systems operate are different from the AM/FM band signals. The AM band operates between approximately 530 KHz and approximately 1710 KHz. The FM band operates between approximately 88 MHz and approximately 108 MHz. RKE frequencies operate between approximately 315 MHz and 433.92 MHz, but are generally centered at approximately 315 MHz and 433.92 MHz. Quality of AM/FM/RKE signals received is directly related to the design of the different antennas used to receive the signals.
In addition to the antenna design having an impact in the quality of the received signals, so too does a splitter used to split the signals received from the antenna(s) being communicated to a radio and RKE system. Because FM and RKE signals operate at RF frequencies in the hundreds of MHz range, the splitter can affect receiving performance of FM and RKE signals if not properly matched to the frequency bands of the respective signals.